Due to environmental and health concerns, there has been a movement toward reducing the amount of volatile organic compounds (VOCs) in paints, stains, and other coating compositions, which evaporate into the environment upon paint film formation. Additives to paints that facilitate or impart desirable paint properties, such as better film coalescence, better resistance to blocking, better film durability, better physical and chemical scrub resistance, and tougher coatings, among others, also contain VOCs. The evaporation of VOCs often results in undesirable aromas, and exposure to such fumes, particularly in areas that are not well ventilated, remains a health concern. Thus, less volatile or non-volatile additives, as well as colorants, that impart comparable (or superior) properties to the paints have been used to replace higher VOC additives. The quest for low VOC paints or a better “green paint” is discussed in a New York Times newspaper article entitled “The Promise of Green Paint” (Kershaw, Sarah, The New York Times, May 15, 2008, p. F6), which is incorporated herein by reference in its entirety.
The reduction of VOC in paints, stains and other coatings and in additives, however, has produced environmentally friendly paints that are more inviting to bacteria, algae, yeasts, fungi and other biological agents that thrive in an aqueous environment. These biological agents grow and die in paint cans and containers, and often impart an unpleasant odor and render paints unusable for its intended purpose, and can cause viscosity loss, discoloration, gassing, frothing, sedimentation and pH changes. Biological agents also present potential health issues. Certain biological agents, such as algae and molds, may grow on dried paint films covering walls or other substrates.
Biocides have been used in aqueous paints or stains to control biological agents inside cans and containers. Some of the biocides may remain on the dried paint film to control algae and molds. However, there is a need to minimize the amount of biocides in aqueous paints or dried paint films while preventing the unimpeded growth of biological agents.